On the summit of Mt Fuji a scale reads about 0.1% lighter
#0015 Science & nature
Fact rank
A
Confirmed with values from a primary source (the 1880 measurement paper). Not S because the measurement is old and a modern summit/foot pair of values was not obtained
Wow rank
A
People may have heard you weigh less on a mountain, but the actual number is a surprise
Usefulness
—
A fact worth knowing for its own sake
Verification: Supported by evidence
AI verification reports the evidence it found; it does not guarantee that a claim is true.
Gravity on the summit of Mt Fuji is about 0.1% weaker than in Tokyo (measured in 1880), so a person who reads 80 kg in Tokyo reads about 80 g lighter at the summit.
Why
Gravity weakens with height.Evidence
Primary Mendenhall, "On a Determination of the Force of Gravity at the Summit of Fujiyama, Japan" (American Journal of Science, 1881). Measured with a pendulum in August 1880: Tokyo 9.7984, summit 9.7886 m/s². The difference is 0.100%, or 80 g for 80 kg (checked by calculation) link
Primary Abstract of a paper in the Journal of the Geodetic Society of Japan (1960). A 1957 measurement gave 978.877 Gal at the summit of Mt Fuji, almost the same as the 1880 value (978.86 Gal) link
Primary Explanation by the Geospatial Information Authority of Japan. At 1,000 m elevation the fourth digit of the gravity value is about 3 lower than at sea level (about 0.03%) link
Notes and limits
Calculating from height alone gives about 0.12% less at 3,776 m, but the mass of the mountain itself pulls downward, so the real difference is smaller. The comparison is with Tokyo, not the foot of the mountain, and includes a small latitude effect (about 0.3°). This applies to spring and electronic scales; a balance shows no difference.
Derivations
Derived from: 体重計の数字は緯度が高いほど大きく出る
Derived facts: 体重が一番軽く出るのはペルーのワスカラン山頂